In 1749, aged 19, he was registered at the students' club for the county of Småland at Uppsala University and got Linnaeus as inspector. The inspector was the head of the university club and was not only responsible for everything to be run properly, but also for helping the students in an active way. As a member of the Småland students’ club Bergius was able to attend the seminars of Linnaeus and also join his excursions at Hammarby.
In 1750 Bergius submitted his first test of learning to Linnaeus, a small preliminary thesis treating the spores of moss - De seminibus muscorum. The theses were usually composed by the professors, but in this case, as a very successful student, Bergius had been allowed to make a contribution himself. Linnaeus had great confidence in his disciple and he was granted a highly coveted scholarship.
Commissioned by Linnaeus
Those who are known as Linnaeus's disciples were mainly his students at the faculty of medicine at Uppsala. The apostles were those who, commissioned by Linnaeus, went abroad to gather plants and natural-history specimens, and who wrote travel books that Linnaeus could make use of. Bergius made two minor journeys commissioned by Linnaeus to Dalarna and Gotland. The journey to Gotland was made in order to gather corals and fossils for Carl Gustaf Tessin's collection of natural-history specimens. The journals from this journey were later handed over to Linnaeus. A journey to the East Indies, to be paid by Queen Lovisa Ulrika, was also contemplated, but for some reason it came to nothing. In his later career Bergius chose to follow his own path as a physician in Stockholm rather than making journeys on behalf of Linnaeus.
Sources: SLÅ 1931, SLÅ 1979-81, Olof Swartz et al. 1822. "Åminnestal över Petr.J. Bergius"